Fuel cells are electrochemical devices that directly convert the chemical energy of a fuel into electricity, and typically employ an anode where the fuel is oxidized, a cathode where the oxidant is reduced, and an ionically conducting membrane as the electrolyte that selectively transports the electroactive ion only.
To minimize resistive loses through the electrolyte and improve fuel cell performance, it is desirable that the ion transporting membrane is made as thin as possible and does not exhibit concominant electronic transport either intrinsically or through the presence of pores and pinholes, both of which may give rise to internal shorting. The latter becomes a critical issue especially for thin film fuel cell structures where even nanometer scale pinholes in the electrolyte membrane may give rise to internal electronic shorting between the anode and cathode, and dramatically diminish the performance of the fuel cell.
Although the first fuel cell was demonstrated more than 150 years ago, followed by a significant development effort and investment by NASA in the 1950s in support of the space program, commercialization of fuel cell technologies have been painstakingly slow. Phosphoric acid fuel cell (PAFC) is the only type of fuel cell to date that has been fully commercialized with over 200 units operating around the globe. The other major types of fuel cells, such as polymer exchange membrane (PEMFC), direct methanol (DMFC), solid oxide (SOFC), Alkaline (AFC), and molten carbonate (MCFC), are all at various stages of development and/or commercialization. Besides the difficulty of matching fuel cell performance and operating conditions with strict materials requirements, the prospects for commercialization of fuel cells have also been plagued with high fabrication and manufacturing costs that make it difficult for these otherwise efficient and environmentally friendly technologies compete economically with conventional power generation systems.
Accordingly, there is a need to develop a fabrication method for ultra thin, large surface area, pinhole free ion conducting membranes on inexpensive substrates to make cost effective, high performance fuel cells with reduced resistive losses and a lowered operating temperature.